Machine for the centrifugal casting of pipes

ABSTRACT

Machine for centrifugally casting pipes having a casting shell and a cooling water jacket coaxial and rotating with the shell. Water is supplied to and discharged from the jacket by way of annular fixed parts coaxial with the jacket. A seal is interposed between each fixed part and the jacket. Each seal comprises a collar connected to rotate with the jacket, a ring freely mounted on the collar with a small radial clearance therebetween and the ring being keyed to the corresponding fixed part. A flexible sealing ring is interposed between the freely mounted ring and the corresponding fixed part.

United States Patent Inventor Andre Pierre Mougin Pont-A-Mousson, France 'Appl. No. 813,075

Filed Apr. 3, 1969 Patented June 29, 1971 Assignee Centre De Recherches De Pont-A-Mousson Pont-A-Mousson, France Priority Apr. 19, 196B France MACHINE FOR THE CENTRTFUGAI I CASTING 0F PIPES 5 Claims, 2 Drawing Figs. 1

- 277/74 lnt.C1 822d 13/10,

. F16j 15/16 Field of Search 164/286- Reierences Cited UNITED STATES PATENTS 2,123,037 7/1938 Carrington 164/297 2,851,289 9/1958 Pedersen 277/70 3,155,393 11/1964 Hummer 277/74 Primary Examiner-J: Spencer Overholser Assistant Examiner-John S. Brown Attorney-J. Delattre-Seguy ABSTRACT: Machine for centrifugally casting pipes having a casting shell and a cooling water jacket coaxial and rotating with the shell. Water is supplied to and discharged from the jacket by way of annular fixed parts coaxial with the jacket. A

seal is interposed between each fixed part and the jacket. Each seal comprises a collar connected to rotate with the jacket, a ring freely mounted on the collar with a small radial clearance therebetween and the ring being keyed to the corresponding fixed part. A flexible sealing ring is interposed between the freely mounted ring and the corresponding fixed part.

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ad Alformey The present invention, due to the work of Mr. Andre lPierre Mougin, relates to machines for the centrifugal casting of metal pipes, in which the rotary casting shell or mold is cooled by the circulation of water in the annular space between the shell or mold and a concentricjacket connected to rotate with this shell.

French Pat. No. 995,993 of Apr. 3, I945 discloses such a machine which comprises four seals directly interposed between the fixed walls of the rotary jacket of the machine, the cooperating elements of these seals, which are respectively fixed to the wall and to the jacket, being applied against each other. Such elements are therefore subjected to wear which is the more rapid as they are more strongly applied against each other, for example by the very pressure of thewater in circulation. Further, the rubbing of the two elements against each other constitutes a brake which absorbs a certain amount of energy and necessitates increasing the power for driving the rotating part, this being the more so as the pressure of the seal on the rotating part is higher. Finally, as the rotating part of the machine is brought to high temperature and the circulation pressure of the cooling water in the jacket is limited so as to avoid exaggerating the wear and the braking effect of each seal, the cooling power of the liquid is limited to a certain temperature, termed the calefaction temperature, beyond which the liquid partially vaporizes in contact with the superheated rotating part.

The object of the present invention is to provide a machine for centrifugally casting pipes, said machine having a rotary shell constituting a mold and a rotary jacket, coaxial with said shell and rotating therewith, for the circulation of cooling water, and fixed annular parts coaxial with the jacket for supplying and discharging water, said machine being so improved as to permit eliminating the aforementioned braking effect and consequently increasing the pressure of the water in the jacket and therefore shifting back the extreme calefaction temperature and affording an improved cooling.

This machine comprises, between each fixed annular part for connection to an outside cooling water circuit and the rotary cooling water jacket, a seal which comprises in combination a collar adapted to rotate with said rotary jacket, a ring freely mounted on said collar with a slight radial clearance, and means for locking said ring relative to the fixed annular part.

in operation, there is established a circulation of water in the slight radial clearance between the rotary collar and the freely mounted ring which thus forms a friction-free hydrodynamic seal.

Further features and advantages of the invention will be apparent from the ensuing description with reference to the accompanying drawing.

In the drawing:

FIG. l is a diagrammatic sectional view of an improved machine for centrifugally casting metal pipes comprising a plurality of seals constructed in accordance with the invention, and

FIG. 2 is a detail view, on an enlarged scale, of one of these seals.

With reference first to FIG. l, which shows diagrammatically and partly a machine for centrifugally casting metal pipes, this machine comprises, in the known manner, a carriage movable in translation. This carriage comprises a case i in which is mounted a rotary shell or mold 2 for centrifugally casting the pipe and having an axis of rotation X-X. This shell 2 is provided with a coaxial jacket 3 which is connected to rotate with the shell. Thisjacket 3 forms with the shell 2 an annular space for the passage of cooling water.

The shell 2 and jacket 3 are driven in rotation by a motor 5.

The cooling water for the shell, provided by an exterior supply circuit, enters and issues at the ends of the carriage by way of pipes 6 connected to this exterior circuit and extending through the case B and opening into one or the other of fixed annular members 7 which are coaxial with thejacket 3 and the shell 2 and have a U-shaped axial radial cross section. The two annular chambers 8 defined by these fixed members 7 communicate with the annular space 4 by way of two openings 9 in the jacket 3 in the region of the pipes 45.

Provided between each flange of each fixed member 7 and the rotaryjacket 3} is a seal 1 F, J and J Each seal, mounted between the jacket 3 and one of the lateral walls of the fixed member '7, is constructed in the following manner (FIG. 2):

A ring 18 is fixed to the transverse wall of the annular member 7. Fixed to this ring lift in an aperture 17 parallel to axis X"*( is at least one key to for another ring or member ll which will be described in detail hereinafter, for rotating relative to the ring lit The key or finger llti extends beyond the fixed ring 18 into a notch 15 in member ill and allows radial and axial movement of the member H.

The combined members '7, l6, and Ni constitute a fixes part relative to which the jacket 3 and shell 2 rotate.

The rotating part of the seal comprises a collar ll) fixed to the jacket 3 near the opening 9. This collar, of very strong material and having a high resistance to corrosion, for example stainless steel, has three stepped outer cylindrical bearing portions [1, b, c which are separated by shoulders d and e. In the presently described embodiment, the portion c has a diameter different from that of the portion a to reduce space consumption.

Freely mounted on the rotating collar lit) is a ring llll having an inner cavity whose shape corresponds to the outer shape of the rotating collar lit). More precisely, the ring ill comprises inner cylindrical'bearing portions a, b, c, with interposed shoulders d and e respectively corresponding to the outer portions a, b, c, of the collar 10 and to the shoulders d and e. The bearing portions of the ring ll have diameters which are slightly greater than the bearing portions of the collar 10, for example the extent of a few tenths of a millimeter, and slightly different lengths so as to form slight radial clearances 1' between the bearing portions and axial clearances j between the shoulders. Thus the clearances i and j constitute a labyrinthlike annular gap between the ring ill and collar 10.

Formed in the bearing portion a of the ring 11 is an annular recess 112 which increases the radial clearance i between the ring ill and the collar 10. Further, provided in the shoulder d of the ring ll is an annular recess 12 increasing the axial clearancej between the ring ill and the collar 10.

Radial recesses M communicate with the recess 13 and put the radial space between the bearing portions a and a in communication with the adjacent shoulders d and d.

Finally, the ring llll comprises an outer cylindrical bearing portion lit which has a diameter substantially less than the inside diameter of the fixed ring 18. Mounted in the large radial space between the fixed ring 11%! and the cylindrical bearing portion H9, is a flexible sealing element 20 for example which has lips applied against the inner face of the fixed ring 13 and the cylindrical bearing portion 19.

The freely mounted ring 111 is preferably of a material having a low coefficient of friction, for example of bronze or synthetic material. For mounting purposes, it is made in two parts interconnected by screws so as to be capable of being fitted on the rotating collar 10.

Each seal is completed by an annular water discharge trough. This trough comprises an inner ring 21 integral with the collar llli and an outer ring 22 capping the ring 21 and integral with the freely mounted ring 11. This outer ring 22 is moreover connected to a water discharge pipe 23 for discharging the water from the outer ring 22.

The machine operates in the following manner:

When the machine is stationary and consequently the shall 2 and the jacket 3 do not rotate and there is not water in the annular space 4, the freely mounted ring 11 bears on the collar 10 through the bearing portions thereof. Consequently, the radial clearance i between the collar 10 and the ring H is larger adjacent the lower generatrices of these bearing portions.

When the water arrives under pressure through one of the pipes 6, it for example flows in the direction of arrowsf in such manner as to pass through one of the annular chambers 8 and the corresponding opening 9 of the jacket 3 and fill the annular space 4 where it constitutes a jacket of water. The water issues in the direction of arrowf continuously by way of the other opening 9 and the second annular chamber 8 and leaves the machine by way of the pipe 6 at the other end of the carriage. With the shell 2 and the jacket 3 stationary, in each seal, the water under pressure moves the lips of the sealing element 19 away from each other and applies them against the inner face of the fixed ring 18 and the outer bearing portion 19 of the freely mounted ring 11.

in the region of the seal, a very small part of the flow of water enters in the direction of arrowj (FIG. 2) the space between the bearing portions 11, issues in the'direction of arrowf and is collected in the trough 21, 22 whence it flows by way of the pipe 23 and is collected in a tank (not shown).

Therefore, water fills the annular space between the bearing portions a, b, c of the collar 10 and the corresponding bearing portions of the ring 11 except for the part of this annular space adjacent the upper generatrices, since it will be understood that the ring 11 bears directly on the collar 10 in this region.

When the shell 2 and the jacket 3 are driven in rotation, both at low speed and then at the centrifugal casting speed which can be several hundreds of revolutions per minute, the layer of water interposed between the bearing portions a, b, c and the shoulders d and e or the collar 10 and the corresponding portions of the ring 11 extends progressively as it rises towards the upper generatrices throughout the perimeter of the bearing portions in accordance with the known process of films of liquid lubricants interposed between a shaft and a bearing bushing. The assembly comprising the collar 10 and the ring 11 thus operates in the manner of a fluid bearing which hydrodynamically supports the ring ll.

More precisely, the distribution of the slight flow of water between the collar 10 and the ring 11 occurs in the following manner: the water enters by way of the radial clearance i, the recess 12 between the bearing portions 0 and a and then the space between the shoulders d and d. By way of the recesses 14 the water fills the recess 13 which widens the space between the shoulders (I and d. The pressure of the portion of water between the collar 10 and the ring 11 decreases by steps in the direction from the bearing portions 11 and a (a few bars) to the bearing portion c and 0' (less than one bar). An increase in the axial length of the recess 12 increases the pressure in the laminated part d, d. By varying the axial length of the recess 12, it is possible to distribute the pressures of the layer of water in such manner that the general result ofthe hydrostatic forces be as small as possible and limited to a safety value, that is, to a value which obliges the faces a, d to separate and therefore maintain an axial clearancej which is always very small, of the order of a few hundredths of a millimeter. Owing to this axial clearance j, the different pressures acting on the face having an outside diameter D of the annular recess l3 and on the diameter D'- of the fixed ring 18, balance each other on each side of the wall of the ring 11, in the same way as the pressures acting on the shoulders d, d and e, e. Under these conditions, the force of contact between the ring 11 and the collar 10 in the space between the shoulders 11, d is very small.

Thus, the layer of water created by the slight leakage flow between the collar 10 and the ring 11 allows this collar 10 to rotate freely relative to the ring 11 without wear of the faces concerned. The wear of the ring ll occurs only when the speed of rotation decreases for stopping the shell and the layer of water becomes thinner adjacent the upper generatrices and allows the corresponding bearing portions to once more come in contact with each other. For this reason, the ring ll is constructed ofa material having a low coefficient of friction.

In the event ofa sudden variation in the pressure in the annular space 4, the pressures also change in the layer of water between the collar 10 and the ring ll. The temporary lack of balance resulting therefrom results in a slight axial displacement towards the right or the left ofthe ring relative to the collar. Consequently, there is a temporary contact between the transverse faces d and 11' until the stepped pressures between the portions a, a and c, c are established at a new hydrostatic equilibrium. During this contact of the faces d, d, the water passes through the recesses 14.

As can be seen, owing to this construction of the hydrodynamic seal, not only the wear is much less than in the rotating seal of known type interposed between a fixed part and a rotating part, but, in the course of rotation, the rotating part is in no way braked by the seal since a layer of water is interposed therebetween. There is therefore a substantial saving in the energy for rotating the shell 2 and the jacket 3.

As the increase in the pressure of the waterjacket 4 has no gripping effect and therefore no braking effect on the rotating part, as occurs in rotating seals of known type, this water pressure can be increased up to the limit of resistance of the material. it can be for example multiplied by six from 0.5 bar to 3 bars and even more. This allows advantageously increasing the cooling effect by pushing back several tens of degrees, for example from l l0 to C. the calefaction temperature, that is, the temperature beyond which gaseous pockets are created in the waterjacket 4 in contact with the hot shell 2.

Owing to the slight clearance between the collar 10 and the ring lit, the hydrodynamic seal can withstand slight radial expansions of the rotating assembly. The same is true of the static seal constituted by the sealing element 20 whose flexibility allows a slight radial compression. This clearance also allows slight axial expansions ofthe rotating part which result in a sliding of the static seal 20 inside the ring. This sealing element also allows radial displacements of the freely mounted ring 11 due to eccentric rotation of the rotating part consisting ofthe shell 2 and the jacket 3 (imperfect circle).

The recesses 14 ensure a constant supply water to the circular recess 13 even when the machine stops operating. They allow the layer of water to fall back at low speeds and at high pressures and in unfavorable cases serve to irrigate the faces and maintain the bearing fluid. This is what occurs when, upon sudden variation in the pressure of the water jacket 4, there is a temporary contact between the collar 10 and the ring 11 on their transverse faces d, d (transitional speed between two different hydrostatic equilibriums).

Although a specific embodiment of the invention has been described, many modifications and changes may be made therein without departing from the scope of the invention as defined in the appended claims.

instead ofa sealing element 26 of the type having lips, there could be provided a flexible sealing washer of another type, for example a toric washer or a washer having a trapezoidal or other cross section adapted to be radially compressed.

Having now described my invention what i claim as new and desire to secure by Letters Patent is:

l. A machine for centrifugally casting pipes, said machine comprising a casting shell having an axis of rotation and a rotary jacket coaxial with and fixed to shell, an annular inner space defined by said jacket and water outlet means in said jacket and in axially spaced relation to said inlet means whereby cooling water can be circulated through said annular space, a first annular fixed part having cooling water supply means associated with said inlet means and a second annular fixed part having water discharge means associated with said outlet means, said annular fixed parts being coaxial with and radially spaced from said jacket, each annular fixed part having an axially inner side and an axially outer side, and a sealing means combined with said inner side of each annular fixed part and said jacket and a sealing means combined with said outer side of each annular fixed part and saidjacket, each seal comprising in combination a collar fixed to said jacket, a ring encompassing said collar and movable relative to the corresponding annular fixed part, said ring and said collar having respectively cooperative inner faces and outer faces defining small clearances constituting an annular labyrinth gap between said ring and said collar, means for preventing said ring from rotating relative to the corresponding fixed part, and a flexible sealing ring interposed between and engaging said corresponding fixed part and said ring, said gap being such that in machine operation cooling water in said annular space is forced into said labyrinth gaps of the sealing means and forms hydrodynamic seals, said sealing rings constituting static seals.

2. A machine as claimed in claim 1, wherein said collar and said ring comprise a plurality of stepped coacting bearing portions defining radial and axial clearances.

3. A machine as claimed in claim 2, comprising an innermost bearing portion and an intermediate bearing portion of said bearing portions of said freely mounted ring, a radially extending shoulder between said innermost bearing portion and said intermediate bearing portion, an annular recess in said shoulder and recesses in said shoulder putting said innermost bearing portion in communication with said annular recess 4. A machine as claimed in claim 3, comprising an annular recess in said innermost bearing portion.

5. A machine as claimed in claim 1, wherein the locking means for locking the ring relative to the fixed annular part comprise a key which is fixed in position in said fixed part and axially and radially movably engaged in a notch in said ring. 

1. A machine for centrifugally casting pipes, said machine comprising a casting shell having an axis of rotation and a rotary jacket coaxial with and fixed to said shell, an annular inner space defined by said jacket and water outlet means in said jacket and in axially spaced relation to said inlet means whereby cooling water can be circulated through said annular space, a first annular fixed part having cooling water supply means associated with said inlet means and a second annular fixed part having water discharge means associated with said outlet means, said annular fixed parts being coaxial with and radially spaced from said jacket, each annular fixed part having an axially inner side and an axially outer side, and a sealing means combined with said inner side of each annular fixed part and said jacket and a sealing means combined with said outer side of each annular fixed part and said jacket, each seal comprising in combination a collar fixed to said jacket, a ring encompassing said collar and movable relative to the corresponding annular fixed part, said ring and said collar having respectively cooperative inner faces and outer faces defining small clearances constituting an annular labyrinth gap between said ring and said collar, means for preventing said ring from rotating relative to the corresponding fixed part, and a flexible sealing ring interposed between and engaging said corresponding fixed part and said ring, said gap being such that in machine operation cooling water in said annular space is forced into said labyrinth gaps of the sealing means and forms hydrodynamic seals, said sealing rings constituting static seals.
 2. A machine as claimed in claim 1, wherein said collar and said ring comprise a plurality of stepped coacting bearing portions defining radial and axial clearances.
 3. A machine as claimed in claim 2, comprising an innermost bearing portion and an intermediate bearing portion of said bearing portions of said freely mounted ring, a radially extending shoulder between said innermost bearing portion and said intermediate bearing portion, an annular recess in said shoulder and recesses in said shoulder putting said innermost bearing portion in communication with said annular recesS.
 4. A machine as claimed in claim 3, comprising an annular recess in said innermost bearing portion.
 5. A machine as claimed in claim 1, wherein the locking means for locking the ring relative to the fixed annular part comprise a key which is fixed in position in said fixed part and axially and radially movably engaged in a notch in said ring. 